Bauschinger effects and work-hardening in spheroidized steels

Abstract

The effects of cementite particles and subgrain boundaries on workhardening behavior of spheroidized carbon steels vere investigated by making direct measurements of residual internal stresses. These internal stresses developed due to plastic incompatabilitiesbetween elastic particles and an elastic-plastic matrix. A continuum analysis of these internal stress fields, based upon a multiple slip model, is presented and is found to be in good accord with the experiments. The internal stresses appear to saturate in the plastic strain range of 3 -5% where a transition in strain-hardening behavior was observed ("double-n" behavior), and to contribute approximately 20% to total work-hardening. The cementite-particle-pinned-subgrain-boundaries, formed during a post-quench annealing treatment, were found to lower the internal stress, thus indicating that they assisted the relaxation processes of entrapped Orowan loops by acting as sources of dislocations. The flow stress increment in dispersion hardened alloys due to work-hardening consisted of internal stress, forest stress, and source-shortening stress.